2 - Electrospun nanofibers

Abstract

Electrospinning is an effective technology for the preparation of nano- and microscale fibers for diverse application in oil recovery, medical devices, and filters. It is achieved by injecting a charged solution of polymeric material through a needle into a region of high electric field. Under these conditions, the expelled jet follows a chaotic, whiplike trajectory toward a grounded collection plate. At low polymer concentrations, the high forces experienced by the jet prior to becoming grounded on the collection plate result in the formation of undesirable discrete droplets of material, rather than fibers. At higher concentrations, above the critical entanglement limit for the polymer, the polymer chains are stretched and orientated, while the solvent rapidly evaporates, delivering high-aspect-ratio fibers. The resulting mesh of overlapping fibers frequently has useful properties such as high surface area and porosity, which has led to their investigation for a range of applications including filtration membranes and tissue scaffolds. One of the major challenges in the development of electrospinning as a manufacturing technology is the use of organic solvents. Typically, fibers are spun from relatively dilute solutions containing 95% solvent. It is clear that systems that use water as a solvent offer many advantages in terms of safety, cost, and sustainability.